U.S. patent number 6,554,801 [Application Number 09/697,571] was granted by the patent office on 2003-04-29 for directional needle injection drug delivery device and method of use.
This patent grant is currently assigned to Advanced Cardiovascular Systems, Inc.. Invention is credited to Mina Chow, Jeffrey Steward.
United States Patent |
6,554,801 |
Steward , et al. |
April 29, 2003 |
**Please see images for:
( Certificate of Correction ) ** |
Directional needle injection drug delivery device and method of
use
Abstract
The invention relates to an apparatus and method for imaging and
mapping various structures located at a target area within a
patient's lumen using conventional IVUS technology. The mapped
images are used to accurately determine and control the location of
the device within the lumen relative to the target area and/or
target site. Once the drug delivery device is properly positioned
within the lumen, additional ultrasonic images are generated and
used to control the position and depth of penetration of a
retractable needle of the device. Needle position can be precisely
determined, both in relationship to the device as well as the
target site for drug delivery. This allows accurate delivery of
drug to the target site and, thus, enhanced treatment
capabilities.
Inventors: |
Steward; Jeffrey (Lakewood,
CO), Chow; Mina (Campbell, CA) |
Assignee: |
Advanced Cardiovascular Systems,
Inc. (Santa Clara, CA)
|
Family
ID: |
24801641 |
Appl.
No.: |
09/697,571 |
Filed: |
October 26, 2000 |
Current U.S.
Class: |
604/164.03;
600/464; 604/22 |
Current CPC
Class: |
A61B
8/12 (20130101); A61M 25/0084 (20130101); A61M
25/104 (20130101); A61M 37/0092 (20130101); A61B
8/445 (20130101); A61B 5/4839 (20130101); A61M
2025/009 (20130101); A61M 2025/0096 (20130101) |
Current International
Class: |
A61M
29/02 (20060101); A61M 37/00 (20060101); A61M
25/00 (20060101); A61M 015/118 () |
Field of
Search: |
;600/407,410-411,424,427,433-435,437,439,440,459-470,101,109,113-116,118
;604/96.01,22,102.01,102.03,158,161,164.01,164.03,164.1,164.11,164.13 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Casler; Brian L.
Assistant Examiner: Thanh; Lofin H.
Attorney, Agent or Firm: Blakely, Sokoloff, Taylor &
Zafman LLP
Claims
What is claimed is:
1. A device for delivering a drug directly to a target site
comprising: an elongate body surrounding an inner lumen and a
needle lumen, wherein said inner lumen surrounds an inner member
and a retractable ultrasonic element wherein said retractable
ultrasonic element is housed within said inner member; a
retractable needle housed within said needle lumen; and an
intravascular ultrasound (IVUS) system connected to a proximal end
of said retractable ultrasonic element.
2. The device of claim 1 wherein said retractable ultrasonic
element further comprises an ultrasound transducer and a co-axial
cable.
3. The device of claim 2 wherein said ultrasound transducer
consists of a piezoelectric crystal having a front surface coated
with a conductive material and a backing material partially
surrounding said crystal.
4. The device of claim 3 wherein said backing material rapidly
reduces piezoelectric oscillations.
5. The device of claim 3 wherein said ultrasound transducer is
covered in a paralyene coating.
6. The device of claim 3 wherein said paralyene coating is a
quarter wave matching layer that couples ultrasonic energy out and
rapidly reduces piezoelectric oscillations.
7. The device of claim 1 further comprising an inflatable balloon
having a proximal end attached to a distal end of said inner lumen
and a distal end of said inflatable balloon attached to a distal
end of said inner member.
8. The device of claim 7 wherein a fluid flows through said inner
lumen to inflate and/or deflate said balloon.
9. The device of claim 1 further comprising a movable guide
wire.
10. The device of claim 9 further comprising: a guide wire lumen
and an ultrasonic element lumen contained within said inner member,
whereby said movable guide wire is housed within said guide wire
lumen and said retractable ultrasonic element is housed within said
ultrasonic element lumen.
11. A device for delivering a drug directly to a target site
comprising: an elongate body surrounding an inner lumen and a
needle lumen, wherein said inner lumen surrounds a retractable
ultrasonic element; a retractable needle housed within said needle
lumen; an intravascular ultrasound (IVUS) system connected to a
proximal end of said retractable ultrasonic element; a movable
guide wire; an inner member contained within said inner lumen,
whereby said inner member houses said guide wire and said
retractable ultrasonic element; and a fluid lumen contained within
said inner lumen.
Description
FIELD OF THE INVENTION
The present invention relates to an apparatus and method for
imaging the position and location of a medical device in a patient.
In particular, the present invention relates to a catheter based
needle drug delivery device having ultrasound imaging technology
that facilitates tracking of the catheter as it is positioned
within the body of a patient.
BACKGROUND
As surgical techniques continue to progress and become less
invasive, an increasing number of medical procedures are performed
with the aid of a catheter. In general, a catheter is a flexible
tube that is inserted into narrow openings within the body and is
used to deliver and/or remove fluids or substances. An example of a
medical procedure that utilizes a catheter is percutaneous
transluminal coronary angioplasty (PTCA).
PTCA is a catheter-based technique whereby a balloon catheter is
inserted into the blocked or narrowed coronary lumen of a patient.
Once the balloon is positioned at the target site, the balloon is
inflated causing dilation of the lumen. The balloon is deflated and
the catheter is then removed from the target site thereby allowing
blood to freely flow through the unrestricted lumen.
Although PTCA procedures aid in alleviating intraluminal
constrictions, such constrictions or blockages reoccur in many
cases. The cause of these recurring obstructions, termed
restenosis, is due to the body's immune system responding to the
trauma of the surgical procedure. As a result, drug therapies are
often applied in combination with the PTCA procedure to avoid or
mitigate the effects of restenosis at the surgical site. The drugs
are delivered to the site via a needle housed within the catheter.
The term "drug(s)," as used herein, refers to all therapeutic
agents, diagnostic agents/reagents and other similar
chemical/biological agents, including combinations thereof, used to
treat and/or diagnose restenosis, thrombosis and related
conditions.
Other procedures, such as those developed to control the effects
and occurrence of angiogenesis, also utilize a catheter having a
drug delivery needle. Angiogenesis is a process whereby new blood
vessels are grown in the body for healing wounds and for restoring
blood flow to tissues after injury or trauma. Angiogenesis occurs
naturally in the body, both in normal states and in disease states.
For example, in females, angiogenesis occurs during the monthly
reproductive cycle to rebuild the uterus lining and to mature the
egg during ovulation. In addition, angiogenic growth factors are
also present during pregnancy to build the placenta and create the
vessels necessary for circulation between the mother and fetus.
Angiogenesis also occurs in various disease states, such as cancer,
diabetic blindness, age-related macular degeneration, rheumatoid
arthritis, coronary artery disease, stroke, and other disorders. In
cases of excessive angiogenesis, the new blood vessels feed
diseased tissues, destroy normal tissues and, with respect to
cancer, allow tumor cells to escape into the circulation and lodge
in other organs. Conversely, insufficient angiogenesis causes
inadequate blood vessel growth thereby impeding circulation which,
in turn, potentially leads to tissue death.
Although angiogenesis occurs naturally in the body, various
procedures have been developed to artificially control the
occurrence and effects of angiogenesis. One such procedure is
Percutaneous TransMyocardial Revascularization (PTMR). PTMR
utilizes a laser catheter to create small channels in the diseased
tissue. The channels re-establish direct blood flow to the tissue
and allow oxygen-rich blood to saturate the oxygen-starved tissue.
PTMR is generally used for the treatment of severe, end-stage
coronary disease.
Another catheter-based procedure used to promote angiogenesis
involves gene therapy. For this procedure, genetic material is
delivered directly to the diseased area of the body via a catheter.
In particular, genetic material, such as Vascular Endothelial
Growth Factor (VEGF), is incorporated into gene delivery vehicles
called vectors, which encapsulate therapeutic genes for delivery to
the diseased cells. Many of the vectors currently in use are based
on attenuated or modified versions of viruses. The vectors may also
be synthetic versions in which complexes of DNA, proteins, or
lipids are formed into particles capable of efficiently
transferring genetic material. A needle injection catheter is used
to deliver the vectors containing the genetic material to the
appropriate cells of the patient in a safe and efficient
manner.
These and other similar catheter-based procedures require accurate
tracking of needle location as the catheter and needle are
maneuvered through the system to the target site in the patient.
Conventional catheter-based needle drug delivery devices utilize
fluoroscopic imaging methods to track catheter and needle movement
in the body of a patient. In general, a radiopaque coating is
applied in a thin, dense layer on a portion of the catheter and/or
needle that is then viewed utilizing a fluoroscope. However, this
method is limited to visualizing device placement within the
artery. This is a limitation when the target for the needle-born
drug/therapy is outside the delivery vessel. Further, this method
produces a planar (two-dimensional image) which may not be
sufficient to accurately steer or track the location of the
catheter through the body of the patient. In addition, due to
inadequate fluoroscopic imaging resolution and limited mass/density
of radiopaque material, these devices are also limited in their
effectiveness to accurately position the catheter needle at the
desired target site.
SUMMARY
In view of the above, there is a need to provide a catheter-based
needle drug delivery device having retractable ultrasonic imaging
features that increases imaging resolution and improves catheter
tracking capabilities. It is also desirable that the catheter-based
needle drug delivery device be used in combination with
intravascular ultrasound (IVUS) technology for mapping needle
position in the body of the patient. In particular, it is preferred
that the ultrasound imaging features of the present device enable a
user of the device to precisely determine needle position in
relation to both the host catheter as well as the vessel wall and
target site for drug delivery.
In accordance with various aspects of the present invention, the
invention relates to an apparatus and method for imaging and
mapping various structures located at a target area within a
patient's lumen using conventional IVUS technology. The mapped
images are used to accurately determine and control the location of
the device within the lumen relative to the target area and/or
target site. Once the drug delivery device is properly positioned
within the lumen, additional ultrasonic images are generated and
used to control the position and depth of penetration of a
retractable needle of the device. Needle position can be precisely
determined, both in relationship to the device as well as the
target site for drug delivery. This allows accurate delivery of
drug to the target site and, thus, enhanced treatment
capabilities.
BRIEF DESCRIPTION OF THE DRAWINGS
The features of the described embodiments are specifically set
forth in the appended claims. However, embodiments relating to both
structure and method of operation are best understood by referring
to the following description and accompanying drawings, in which
similar parts are identified by like reference numerals.
FIG. 1 is a perspective view of a catheter based needle drug
delivery device and ultrasound imaging system;
FIGS. 2a-2e are cross-sectional views of various embodiments of a
catheter based needle drug delivery device;
FIG. 2f is a detailed cross-sectional view of the distal portion of
the device of FIGS. 2a-2e;
FIG. 3 is a detailed cross-sectional view of the ultrasound
transducer of FIG. 2f;
FIG. 4 illustrates one embodiment of the catheter based needle drug
delivery device positioned within a lumen;
FIG. 5 illustrates the ultrasound field wave generated by the
device of FIG. 4;
FIG. 6 illustrates one embodiment of the display, imaging and
stacking functions of an IVUS system;
FIG. 7 is a cross-sectional view of a lumen;
FIG. 8 illustrates a method of using the device of FIG. 4;
FIG. 9 illustrates one embodiment of the image of the lumen and
device of FIG. 4;
FIG. 10 illustrates an alternate embodiment of the image of the
lumen and device of FIG. 4; and
FIG. 11 illustrates another embodiment of the image of the lumen
and device of FIG. 4.
DETAILED DESCRIPTION
An exemplary catheter-based needle drug delivery device 10 and
ultrasonic imaging display system 12 are shown schematically in
FIG. 1. The imaging display system 12 includes an image processor
having a display 14 and a signal processor 16. Both the image
processor 14 and signal processor 16 are general purpose processors
of the type that are commonly used in connection with devices
similar to that of the present invention. Additional disclosure of
the ultrasonic imaging system 12 is discussed in further detail
below.
FIGS. 2a and 2b show cross-sectional views of the catheter-based
needle drug delivery device 10. In general, the device 10 includes
an elongate body 18 that surrounds a needle lumen 82 and an inner
lumen 22. Housed within the inner lumen 22 are a fluid lumen 24 and
an inner member 26 that also contains a guide wire lumen 44 and
ultrasonic element lumen 50. An inflatable balloon 28 is attached
to the inner lumen 22 and the inner member 26. In general, the
proximal end 30 of the balloon 28 is attached to a distal end 32 of
the inner lumen 22 and the distal end 34 of the balloon 28 is
attached to the distal end 36 of the inner member 26. In the spirit
of convenience and brevity, the device referenced in the text and
figures of the present disclosure is configured according to the
above-described design. However, it should be noted that other
designs of the catheter-based needle drug delivery device are also
within the scope of the claimed invention.
For example, in another embodiment of the device shown in FIG. 2c,
both the guide wire 46 and retractable ultrasonic element 52 are
housed within a single lumen, i.e. the inner member 26. The
elongate body 18 surrounds an inner lumen 22 and a needle lumen 82.
Housed within the inner lumen 22 are an inner member 26 and a fluid
lumen 24. The inner member 26 surrounds the guide wire 46 and
retractable ultrasonic element 52. An inflatable balloon 28 is
attached to the inner lumen 22 and the inner member 26. In general,
the proximal end of the balloon 28 is attached to the distal end of
the inner lumen 22 and the distal end of the balloon 28 is attached
to the distal end of the inner member 26.
In yet other embodiments of the device, shown in FIGS. 2d and 2e,
the inner lumen 22 also serves as the lumen through which fluid
flows to inflate and/or deflate the balloon 28. As such, the
separate fluid lumen, described above, is omitted from the
catheter-based needle drug delivery device 10. Thus, the inner
lumen 22 functions as a fluid lumen in addition to housing the
guide wire lumen 44 and ultrasonic element lumen 50. Alternatively,
the inner lumen 22 functions as a fluid lumen and also contains the
guide wire 46 and retractable ultrasonic element 52.
The structure of the inflatable balloon 28 is similar to those well
known to those having ordinary skill in the art. The inflatable
balloon 28 may be used for various procedures including, but not
limited to, opening narrowed passageways, distributing drugs to
specific target sites, and delivering/positioning stents or other
medical devices within the lumen. The term "target site," as used
herein, refers to sites/areas both inside and outside the
vessel/lumen. The inflatable balloon 28 is located at the distal
end 38 of the device 10 and is initially deployed in a low profile,
deflated condition. When the balloon 28 is positioned at the target
site it is inflated with fluid via the inflation port 40 located
near the proximal end 42 of the device 10. During inflation of the
balloon 28, fluid flows from the inflation port 40, through the
fluid lumen 24, and to the balloon 28. In addition, the fluid flows
through the same lumen 24, but in the opposite direction, upon
deflation and subsequent removal of the balloon 28.
Extending partially along the length of the device 10 is the inner
member 26. As shown in FIGS. 2a-2e, a portion of the inner member
26 protrudes out the distal end 34 of the balloon 28. Housed within
and along the length of the inner member 26 are two lumens. The
first lumen 44, i.e. the guide wire lumen, provides a passageway
for a movable guide wire 46. The guide wire 46 extends from beyond
the distal end 38 of the device 10 to a guide wire exit 48 located
near the proximal end 42 of the device 10. The guide wire 46 serves
as the steering mechanism of the device 10 and enables an operator
to maneuver the device 10 through the various vessels and lumens of
the patient to the chosen target site. Overall length and diameter
of the guide wire 46 are within the range of approximately 74.8
inch to 118.1 inch (190 cm to 300 cm) and 0.0152 inch to 0.019 inch
(0.0386 cm to 0.0483 cm), respectively. The guide wire 46 may be
fabricated from a variety of materials including, but not limited
to, stainless steel, Nitinol.TM., platinum and polymers. These and
other similar materials exhibit the required structural properties,
such as strength and flexibility, desired in guide wire elements
46.
The second lumen 50, i.e. the ultrasonic element lumen, of the
inner member 26 houses the retractable ultrasonic element 52 of the
device 10. As shown in FIGS. 2b and 3, the distal end of the
ultrasonic element 52 has an ultrasound transducer or transducer
array 54 and the proximal end contains the associated co-axial
cable 56 that connects to the imaging display system 12 (i.e. IVUS
imaging system). In general, ultrasonic waves generated by the
ultrasonic element 52 impinge on the surface of the target area.
The timing/intensity of the ultrasonic waves reflected back to the
transducer 54 differentiates between the various anatomic
boundaries or structures of the target area. The waves detected by
the transducer 54 are converted to electric signals that travel
along the coaxial cable 56 to the imaging system 12. The electrical
signals are processed and eventually arranged as vectors comprising
digitized data. Each vector represents the ultrasonic response of a
different angular sector of the target area and/or bodily lumen. As
such, the amplitude of the reflected ultrasonic waves/electric
signals is displayed as variable shades of, for example, gray on
the display. Thus, anatomic structures with different acoustic
density are portrayed with varying degrees of brightness, resulting
in a visible, displayed image of the various structures within the
body.
The coaxial cable 56 of the ultrasonic element 52 contains an
insulated solid or stranded center conductor 58 (e.g., a wire)
surrounded by a solid or braided metallic shield 60, wrapped in a
plastic cover or jacket 62. The wire 58 is the primary conductor,
whereas the shield 60 is used for ground. The insulation 64
surrounding the wire 58 is typically made of a dielectric material,
such as polyester or plastisol, and functions to sustain the
current traveling within the wire 58 with minimal dispersion. A
conductive material 66, for example copper, gold, palladium,
conductive epoxy, or other similar materials, is used to attach and
electrically connect the distal end of the coaxial cable 56 to the
ultrasound transducer 54.
The ultrasound transducer 54 has a piezoelectric crystal 68
configured for optimal acoustic output efficiency and energy
conversion. In some embodiments, the crystal 68 is made of PZT or
lead-ceramic materials, such as PbTiO.sub.3 (lead titanate) or
PbZrO.sub.3 (lead zirconate). As shown in FIG. 3, the back surface
70 of the piezoelectric crystal 68 is coated with conductive
material plating such as gold, platinum or palladium, and other
similar conductive materials. The gold plating provides a
sufficient electrical contact to the back 70 of the piezoelectric
crystal 68 to connect with the wire 58 of the coaxial cable 56. A
conductive epoxy 72 is used to mechanically and electrically attach
or connect the coaxial center conductor 58 to the back 70 of the
piezoelectric crystal 68. In addition to conductive epoxy 72,
solder joints, cold solders, ultrasonic welds and other similar
attachment techniques can also be used.
The front surface 74 of the piezoelectric crystal 68 is also coated
with conductive material plating. The front surface plating
electrically connects the front surface 74 of the crystal 68 to the
coaxial shield 60 through the conductive material 66. Partially
surrounding the crystal 68 and its related components is a backing
material 76. The backing material 76 serves as a non-conductive
sound absorbing material that eliminates sound waves coming off the
back 70 of the piezoelectric crystal 68. In addition, the backing
material 76 also facilitates rapid reduction in piezoelectric
oscillations.
To electrically isolate the ultrasound transducer 54, the
transducer 54 is covered in a paralyene coating 78. The paralyene
coating 78 is a quarter wave matching layer that does not interfere
with the acoustic output or response of the piezoelectric element.
In addition, the paralyene electrically isolates the two sides of
the piezoelectric crystal and associated electrical
connections.
As shown in FIGS. 2a and 2b, the device also includes a retractable
needle 80 housed in the needle lumen 82 and freely movable therein.
The hollow, tubular shaped needle 80, having an inner diameter
within the range of approximately 0.002 inch to 0.010 inch
(5.1.times.10.sup.-3 cm to 25.4.times.10.sup.-3 cm) and an outer
diameter within the range of approximately 0.004 inch to 0.012 inch
(10.2.times.10.sup.-3 cm to 30.5.times.10.sup.-3 cm) provides a
fluid conduit that extends from the proximal end 84 to the distal
end 86 of the needle 80. The distal end 86 of the needle 80
terminates in a curved, tissue piercing tip having an angle of
curvature between 30 degrees to 90 degrees. Needle curvature
facilitates placement of the needle tip near to or within the
desired target tissue. Further, to allow easy needle deployment
from and retractability into the lumen, yet provide sufficient
structural strength for insertion into tissue, the needle 80 is
preferably fabricated from, for example, stainless steel, NiTi
(nickel titanium), platinum or other similar semi-rigid materials.
The needle can also be coated with fluoroscopically opaque
materials to enhance its imaging capabilities on the
fluoroscope.
Near the proximal end 84 of the needle 80, the needle 80 connects
to an adapter 86 that attaches the needle 80 to a needle lock 88
and a needle adjustment puncture knob 90. The needle lock 88 is
used to secure the needle 80 in place and prevent further movement
of the needle 80 within the lumen once the needle 80 is located in
the desired position. A needle adjustment knob 90 controls accurate
needle extension out of the distal end of the catheter and depth of
penetration into the tissue target. In general, the needle
adjustment knob 90 is slidable along a proximal portion of the
needle lumen or element 89 housing the needle 80. The element 89
includes various gradations or scalable markings along a portion of
its length that correspond to the length of needle 80 extending out
from the needle lumen 82. During use, the needle adjustment knob
90, that is also attached to the proximal end of the needle 80, is
locked into position at a marking corresponding to the desired
length of needle extension from the catheter. The knob 90 is then
moved in a distal direction until it butts against the needle lock
88. Movement of the knob 90 also moves the needle 80, so that the
predetermined length of needle 80 extends out from the needle lumen
82. The needle lock 88 is then used to secure the needle 80 in
place and prevent further movement of the needle 80 within the
lumen.
Located near the proximal end 42 of the device 10 is a drug
injection port 92. The port 92 provides a connection for various
dispensing elements such as a syringe, fluid pump, etc. In addition
to drugs, other fluids including, but not limited to, therapeutic
agents and diagnostic substances, may also be injected into the
port 92 for delivery to the target site. Fluids injected into the
port 92 travel through the needle 80 and are dispensed from the
distal tip of the needle 80.
In an alternate embodiment, the needle 80 can also be used to
aspirate fluid from tissues. A negative pressure or suction is
applied at the drug injection port 92. The resulting pressure
differential within the lumen 82 of the needle 80 causes tissue
fluid to be drawn into the tip of the needle 80. The fluid travels
toward the proximal end 84 of the needle 80 and is collected at the
injection port 92 site for further analysis.
Method of Use
The retractable ultrasonic element 52 of the drug delivery device
10 allows the various structures located at a target area within a
patient's lumen to be imaged and mapped using conventional IVUS
technology. The mapped images are used to accurately determine and
control the location of the device 10 within the lumen relative to
the target area and/or target site. Generally, the target area
and/or target site is the narrowed or diseased portion of the lumen
requiring drug therapy. Once the drug delivery device 10 is
properly positioned within the lumen, additional ultrasonic images
are generated and used to control the position and depth of
penetration of the retractable needle 80. As such, needle position
can be precisely determined, both in relationship to the device 10
as well as the target site for drug delivery. This allows accurate
delivery of drug to the target site and, thus, enhanced treatment
capabilities.
During use of the device 10, the distal end 38 of the device or
catheter 10 is inserted into the lumen of the patient and guided to
the target area, i.e. narrowed area due to plaque buildup, via
conventional methods. As shown in FIG. 4, the distal end 38 of the
catheter 10, in particular the retractable ultrasonic element (not
shown), is positioned near the target site 94 of the patient's
lumen 96. In one embodiment, the retractable ultrasonic element is
positioned distal to the target site 94 of the patient's lumen. The
target area 95 is then imaged using IVUS technology. In general, a
signal, in the form of a voltage pulse, generated by the signal
processor of the IVUS system (not shown) travels through the
coaxial cable to the ultrasound transducer of the ultrasonic
element. The voltage pulse results in an electromotive force that
causes the crystal of the transducer to oscillate, thereby
producing sonic waves.
As shown in FIG. 5, the ultrasonic waves 98, forming an energy
waveform field, emanate from the ultrasound transducer (not shown)
into the surrounding tissues and structures. Waves reflected by
tissues, or other structures in the lumen 96 near the target area
95, and detected by the ultrasound transducer are converted back to
electric signals. The signals travel along the coaxial cable to the
imaging system where they are then processed. As a result, a first
axial, cross-sectional image of the various structures is generated
and displayed on the IVUS system. The image that appears on the
display is then adjusted and optimized, in terms of gain, zoom, and
other related resolution variables.
To obtain a mapped, longitudinal view of the lumen 96, the distal
end of the ultrasonic element 52 is slowly moved in the proximal
direction. Movement of the ultrasonic element 52 may be either
manually and/or automatically controlled. Approximately hundreds of
cross-sectional images are generated, similar to the
above-described single-image procedure, and then stacked in real
time. FIG. 6 representatively illustrates the imaging and stacking
functions performed by an IVUS system. A single, cross-sectional
image 100 of a lumen 96 is displayed on the monitor 14. Additional
cross-sectional images 102, generated as the ultrasonic element 52
(not shown) is slowly moved through the lumen, are shown in hatched
lines. These images 102 are collected and processed, or stacked, by
the system in real-time mode. The developing longitudinal view 104
of the lumen 96 (also shown in hatched lines) as the ultrasonic
element 52 is moved through the lumen 96 can also be displayed on
the monitor 14 of the IVUS system. Therefore, the IVUS system can
either display a two-dimensional cross-sectional image of the lumen
96 or a three-dimensional longitudinal view of the lumen 96.
In general, a vascular or arterial image consists of three layers
that make up the walls of the lumen 96. As shown in FIG. 7, the
inner-most radial layer 106, which, for example, surrounds the
hollow channel 108 of the lumen 96 through which blood flows,
contains endothelial cells. White blood cells migrate from the
bloodstream into the endothelial cells of the lumen 96 and are
transformed into cells that accumulate fatty materials. The
accumulated materials 110, also termed plaque, continue to build
within the lumen. As the plaque 110 thickens, the channel 108
within the lumen 96 narrows. The plaque 110 may further occlude the
lumen 96 until it is completely closed or it may detach and float
downstream, causing an obstruction elsewhere.
Surrounding the endothelial cells is a layer of smooth muscle cells
112. In addition to reducing the lumen opening 108, the plaque 110
may also stimulate smooth muscle growth 112. Proliferation of
smooth muscle cells 112 further contributes to decreasing the size
of the lumen opening 108. The outermost layer 114 of the lumen 96
is termed the adventitia. In general, the function of the
adventitia is to provide nutrients to the vessel wall.
In an alternate embodiment, the internal lumen 96 may also be
imaged by initially positioning the tip of the ultrasonic element
52 proximal to the target area 95. As such, a longitudinal view of
the lumen 96 may be obtained by slowly pushing the ultrasonic
element 52 in the distal direction until the tip of the ultrasonic
element 52 is located distal to the target area 95. In another
embodiment, the ultrasonic element 52 is pushed and/or pulled
repeatedly across the target area 95 to obtain numerous detailed
images and views of the lumen 96 and structures within the lumen
96. Other areas or structures of interest within the lumen 96 may
also be investigated using the methods described above.
In addition to displaying the internal surface of the lumen 96, the
device 10 is also used to accurately determine catheter position
with respect to the target site 94 within the lumen. In addition to
specifically targeting the desired regions of the lumen 96, the
transducer 54 is also used to accurately track the position and
location of the retractable needle 80. Therefore, both the exact
location and depth of needle penetration are determined with the
device 10.
By imaging the target area 95 of the lumen 96, a user of the device
is able to precisely identify the desired injection site. As
previously explained, angiogenesis, restenotic drug therapies and
other related procedures require injections of various fluids
including, but not limited to, therapeutic agents, diagnostic
reagents, and genetic material, whereby the fluids are delivered
directly to the diseased area of the lumen 96. Ultrasonic imaging
enables device users to track needle movement and penetration into
tissue.
The imaging technique requires an initial imaging of the target
area 95. As shown in FIG. 8, the retractable ultrasound element
(not shown) of the device 10 maps the inner surface of the target
area 95 adjacent to the balloon (not shown) with the aid of a
conventional IVUS system 12. In addition, the position of the
retractable needle (not shown) is also mapped using the same
ultrasound element and IVUS system 12. FIG. 9 illustrates one image
of the catheter and retractable needle 80 within the lumen 96 as
mapped using the ultrasound technique. The differential density
between the needle material and the target tissue results in a
discrete and easily identifiable IVUS signal. As such, needle
position can be precisely determined, both in relationship to the
host catheter 10 as well as the target site 94 for drug
delivery.
Since the size of the catheter 10 and its components are known,
accurate calculations and measurements can be made of the
structures within the lumen 96. When the needle 80 is optimally
positioned at the target site 94, the balloon 28 is inflated with
fluid. As shown in FIG. 10, the inflated balloon 28 securely
situates the catheter 10, and thereby the needle 80, within the
lumen 96. The inflated balloon 28 also prevents the catheter 10
from sliding out of position when the needle 80 is inserted into
the tissue. In general, as the needle 80 is advanced out of the
needle lumen 82 and contacts the tissue surface, the resistance of
the tissue to needle penetration has a tendency to force the
associated catheter 10 in a direction approximately opposite to the
direction of needle advancement/penetration. However, the friction
between the inflated balloon 28 contacting the tissue surfaces
prevents movement of the catheter 10 in the opposite direction. Due
to the added support from the balloon 28, the needle 80 is allowed
to advance and thereby penetrate the tissue. As shown in FIG. 11,
the depth of needle penetration can be easily calculated using the
ultrasonic image. As such, the needle 80 can be extended a
predetermined depth into the tissue and/or target site 94. This
allows accurate delivery of, for example, drug to the target area
95 and, thus, enhanced treatment capabilities.
After the desired amount of drug is delivered to the target site
94, the needle 80 is retracted and removed from the tissue. The
fluid is also removed from the balloon 28 so that the balloon 28
returns to a low profile, deflated state. At this point, the device
10 may be repositioned at an alternate target site 94 for
additional drug delivery according to the above-described
procedure. Alternatively, upon completion of the procedure, the
device 10 may simply be removed from the lumen 96 of the
patient.
Although the invention has been described in terms of particular
embodiments and applications, one of ordinary skill in the art, in
light of this teaching, can generate additional embodiments and
modifications without departing from the spirit of or exceeding the
scope of the claimed invention. Accordingly, it is to be understood
that the drawings and descriptions herein are proffered by way of
example to facilitate comprehension of the invention and should not
be construed to limit the scope thereof.
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